De la microstructure à l’archéologie expérimentale: comprendre les savoir-faire antiques des fabricants des monnaies en alliages cuivreux.

Abstract

The advent of the die-casting technique for coin flan production at the beginning of the Hellenistic period marked a significant advancement over previously employed methods. This innovation could have led to its widespread adoption throughout the Mediterranean basin. However, an in-depth metallurgical study (metallography and elemental analysis) conducted on a large sample of ancient copper alloys coins revealed that the majority of them were recrystallized. This result, contradicting the initial hypothesis of systematic diffusion, calls into question the commonly accepted production sequence. Experimental archaeology sessions have made it possible to implement various thermal or mechanical treatments that may have been used in the ancient coin manufacturing process. Several key steps in the process, such as quenching, hot striking (still debated today), the production of flans from rods or billets, and overstriking, require further investigation. These experiments have notably made it possible to establish a microstructure reference database. They have thus shed new light on certain practices, such as hot striking, which seems never to have been employed, as indicated by the presence of numerous cracks in the microstructure of the samples and the formation of thick oxide layers on the surface of the coins, causing them to lose their characteristic golden luster. Moreover, the technique of manufacturing flans from rods, which involves multiple passes of hammering and annealing, raises new questions about the interest in developing such complex processes and the internal organization of minting workshops.